1. Field of the Invention
The present invention generally relates to the field of image processing, and more particularly relates to an object positioning method and an object positing device on the basis of object detection results obtained by plural stereo cameras.
2. Description of the Related Art
At present, a technique carrying out detection and positioning with respect to an object by utilizing a single stereo camera is well known. For example, a paper titled as “Stereo Person Tracking with Adaptive Plan-View Templates of Height and Occupancy Statistics” written by Michael Harville in 2003 discloses this kind of technique.
However, if only one stereo camera is utilized, the view angle of detection is limited, and the rate of detection is not high enough. As a result, plural stereo cameras have been employed for carrying out detection and positioning with respect to an object recently. By using the plural stereo cameras, it is possible to increase the coverage of detection, and more importantly, it is possible to improve the accuracy of detection. However, up to now, the research on how to use the plural stereo cameras to carry out detection and positioning with respect to an object has not been well conducted.
One of the key problems when the plural stereo cameras are employed to carry out detection and positioning with respect to an object is how to merge the results obtained by the plural stereo cameras. When the plural stereo cameras are used to carry out detection and positioning with respect to an object, the view angles of the plural stereo cameras may overlap so that some areas may be captured by more than one stereo camera. That is to say, since each of the plural stereo cameras performs detection and positioning on an object separately, when the object is captured by the plural stereo cameras, it is necessary to conduct a merging process for achieving the combination of the detection results of the same object detected by the respective stereo cameras so as to get a final detection result.
At present, regarding how to carry out the merging process, there are some conventional methods. One of them is performing comparison on the distances between objects on the basis of the detection results obtained by different stereo cameras. If the distances between the objects are very close, then the objects are regarded as corresponding to a same object; otherwise, the objects are regarded as corresponding to different objects. However, in general, since there is an error between a detection result (i.e., a detected position) and its corresponding true position, this kind of method has some problems as shown in FIGS. 1A and 1B as well as FIG. 2.
FIG. 1A illustrates, in the world coordinate system, the detection results of objects in a predetermined space acquired by two stereo cameras. As shown in FIG. 1A, two small triangles on the top and the bottom respectively represent the positions of the two stereo cameras, and two lines (each of them is formed by plural line segments) therein respectively represent the viewing fields of the two stereo cameras. In addition, small circles therein represent the object detection results obtained by one of the two stereo cameras, and black spots therein represent the object detection results obtained by another one of the two stereo cameras. Obviously, the corresponding true result should be that there are four objects in the predetermined space. FIG. 1B illustrates a merging result obtained by adopting a conventional merging method. In FIG. 1B, each of black rhombuses represents a position of a merged object. As a result, according to FIG. 1B, it is apparent that one merged object is incorrectly merged, i.e., one true object becomes two detected objects.
FIG. 2 illustrates, in the world coordinate system, the detection results of objects in a predetermined space detected by two stereo cameras. Similar to FIG. 1A, two small triangles on the top and the bottom in FIG. 2 respectively represent the positions of the two stereo cameras, and two lines (each of them is formed by plural line segments) respectively represent the viewing fields of the two stereo cameras. In addition, small circles therein represent the object detection results of one the two stereo cameras, and black spots therein represent the object detection results of another one of the two stereo cameras. According to FIG. 2, it is obvious that in a small range therein, there are three small circles and two black spots are very close to each other. In this kind of case, it is very difficult to determine to which objects the three small circles and the two black spots correspond.
As a result, it is necessary to develop a kind of technique by which the above-described problems can be avoided when carrying out detection and positioning with respect to an object by employing plural stereo cameras, so as to be able to accurately detect and locate the object.